In the decade she has served on the Second Circuit Court of Appeals — the busiest appellate court for business and financial matters in the nation — Judge Sonia Sotomayor has authored some 150 civil and business cases and voted on hundreds more. But many lawyers and scholars who have examined her record closely say that her opinions in this field are unpredictable, and do not put her clearly in a pro- or anti-business camp.

In a 2006 property rights case, she upheld a town’s effort to take private property for redevelopment. But in 2002, she supported property rights in a case involving impounded cars.

A 2006 case in which she allowed class-action lawsuits against Merrill Lynch suggested to some business lawyers that she was amenable to lawsuits against big corporations. But in a 2006 securities case against the same company, she voted with the majority in refusing to allow a class to be formed.

“It’s impossible to look at these decisions and say, oh, all of these results clearly reflect a pre-existing, across the board bias one way or another,” said Andrew J. Pincus, an lawyer who has argued many commercial cases before the Supreme Court.

Some conservatives have pointed to individual opinions and asserted that they show dire times ahead for business if Judge Sotomayor is confirmed. Michael Greve, an American Enterprise Institute scholar, writing in National Review Online, placed Judge Sotomayor “among the most aggressively pro-plaintiff, anti-business appellate judges in the country.”

But others who have examined Judge Sotomayor’s work say the opinions reveal a practical streak. “She does seem to take every one as it comes,” Mr. Pincus said, an approach he compared to that of Justice David H. Souter. He said she issues business opinions that hew closely to the precedents of her circuit and of the Supreme Court.

There is no single factor that businesses look for in a jurist, though in general the financial world would like to see fewer lawsuits. So a tendency to allow suits against businesses to go forward is a worrying sign to pro-business interests, said Jonathan Adler, a law professor and director of the Center for Business Law and Regulation at Case Western Reserve University School of Law in Cleveland. But he cited a few cases that might raise red flags for the financial world, including these:

¶Riverkeeper v. E.P.A., a 2007 case in which Judge Sotomayor ruled that the Environmental Protection Agency should not have weighed costs against environmental benefits in requiring water intake structures for power plants that protect fish. The Supreme Court overruled that decision in April by a vote of 6 to 3.

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Judge Sonia Sotomayor upheld a towns effort to seize property. Bart Didden stood on property that had been condemned.Credit
Janet Durrans for The New York Times

¶In a securities case, Judge Sotomayor interpreted a 1998 federal law intended to limit class-action lawsuits in a way that allowed such suits. In 2006, the Supreme Court reversed Judge Sotomayor’s opinion in the case, Merrill Lynch v. Dabit, by a vote of 8 to 0, and archly called the logic allowing the exemption “odd, to say the least.”

¶In Malesko v. Correctional Services, Judge Sotomayor found that a legal theory that allows plaintiffs to sue the government over misconduct could be applied to a private company operating under a government contract. The Supreme Court reversed the ruling by a vote of 5 to 4.

¶And in a key property-rights case, Didden v. Village of Port Chester, Judge Sotomayor took part in a brief unsigned order from the Second Circuit in 2006. The order, which followed the Supreme Court’s major property-taking decision in Kelo v. City of New London, supported a town’s effort to seize property for the use of a developer. Richard A. Epstein, a conservative legal scholar at the University of Chicago, wrote in Forbes magazine that “American business should shudder in its boots if Judge Sotomayor takes this attitude to the Supreme Court.”

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Other legal scholars argue, however, that for any case that conservatives deplore, there is a counterexample. For example, Joseph A. Grundfest, a former commissioner of the Securities and Exchange Commission, contrasted the Merrill Lynch case with a similar one in which Judge Sotomayor voted on the company’s side. Taken together, he said, the two cases suggest that “this judge can’t be neatly pigeonholed as pro-plaintiff or pro-defendant in securities litigation matters.”

Ilya Somin, an assistant professor of law at George Mason University who has written critically about the decision in the property-rights case, said Judge Sotomayor “does deserve some substantial credit” for a 2002 case in which she struck down New York City’s policy of seizing vehicles in certain offenses.

Some of the attacks against the judge’s business rulings turn a complex legal record into a caricature, said Walter K. Olson, a senior fellow at the Manhattan Institute, a conservative organization, and the editor of a blog, Overlawyered.com. While expressing some qualms about Judge Sotomayor’s views, Mr. Olson said “she will not be as liberal as many of the Republicans are saying — but no one could be that liberal, even if they tried.”

Jill E. Fisch, a professor at the University of Pennsylvania Law School and an expert in securities regulation, suggested that in such areas of specialization, Judge Sotomayor’s opinions tend to be “fairly technical and restrained,” but without the flair of a jurist who feels deeply one way or another about the topic.

“I don’t see this as one of her core interests,” she said, suggesting that in such cases the judge might “look at the letter of the law, and follow the leadership of those who have more passion for those questions.”

Politics has become a poor predictor in business law, said Thomas H. Dupree Jr., a lawyer who has argued cases before Judge Sotomayor and who served in the Justice Department in the administration of President George W. Bush. The Supreme Court has largely “de-politicized” many business cases, he said, pointing to the contentious issue of punitive damages, opposed by business. Recent theories of constitutional restrictions on punitive damages have arisen from the more liberal wing of the court, even though the rulings protect business. In such an unpredictable environment, he suggested, Judge Sotomayor might fit right in.

A version of this article appears in print on , on Page A16 of the New York edition with the headline: Sotomayor’s Appellate Opinions Are Unpredictable, Lawyers and Scholars Say. Order Reprints|Today's Paper|Subscribe